TW202222946A - Structure for manufacturing cast article - Google Patents

Abstract

This structure for manufacturing a cast article includes an organic component at least a portion of which is an organic fiber. When heated for 30 minutes at 1000 DEG C in a nitrogen atmosphere, this structure has a mass reduction rate of 1 mass% to less than 20 mass%. The structure for manufacturing a cast article includes inorganic particles. The structure for manufacturing a cast article includes, as the inorganic particles, first inorganic particles having at least one of a prescribed shape and a prescribed property, and second inorganic particles having at least one of a prescribed shape and a prescribed property different from that of the first inorganic particles. Additionally or alternatively, the structure for manufacturing a cast article has a maximum bending stress of 9 MPa or greater and a bending strain of 0.6% or greater under maximum bending stress, as measured in accordance with JIS K7017.

Description

Structures for Casting Manufacturing

The present invention relates to a structure for manufacturing a cast product.

A wood mold, a metal mold, or a sand mold is typically used for casting molds, and these molds are desirably improved in formability and shape retention, lightweight, and reduced in disposal cost. The present applicant proposes a structure for producing a cast, which contains inorganic fibers, a layered clay mineral, and inorganic particles other than the layered clay mineral, and has an organic component content of a specific amount or less (Patent Document 1). prior art literature Patent Literature

Patent Document 1: US 2020346279 A1

The present invention relates to a structure for manufacturing a cast product. In one Embodiment, the said structure contains an organic component. In one embodiment, at least a part of the organic component in the structure is an organic fiber. In one embodiment, the mass reduction rate of the structure after heating at 1000° C. for 30 minutes in a nitrogen atmosphere is 1 mass % or more and less than 20 mass %. In one embodiment, inorganic particles are contained. In one embodiment, the inorganic particles include first inorganic particles that are non-layered particles and second inorganic particles that are layered particles. In one embodiment, the inorganic particles include first inorganic particles having a melting point of 1200°C or higher, and second inorganic particles having a melting point of less than 1200°C. In one embodiment, the maximum bending stress measured according to JIS K7017 is 9 MPa or more. In one embodiment, the bending strain at the maximum bending stress measured in accordance with JIS K7017 is 0.6% or more.

Although the structure described in Patent Document 1 has high formability and shape retention, it is concerned with improving the workability of processing and assembling the structure at the time of casting mold production, and reducing the amount of organic materials contained in the structure during casting. There is still room for improvement in the gas defects of the castings caused by the combustion gases and the reduction of metal penetration on the surface of the castings.

Therefore, the present invention relates to a structure for producing a cast product that achieves both improved workability, reduction of gas defects, and reduction of metal penetration on the surface of the cast product.

Hereinafter, the present invention will be described based on its preferred embodiments. The structure for casting production of the present invention (hereinafter, also simply referred to as "structure") is suitably used as a split mold or casting mold for casting. In this specification, depending on the context, the "structure for casting production" or "structure" refers to a member constituting a member of a casting mold, for example, a split mold, and the casting mold itself. The "mass %" in this specification means the mass ratio with respect to the whole mass of the structure for casting manufacture unless otherwise specified.

In the following description, for convenience of description, the structure body for casting product production, which is a constituent member of a casting mold to which coating or the like to be described later is not performed, will be described. In addition, when the structure has a plurality of constituent members or is formed of a plurality of layer structures, the following description applies to any constituent members or layer structures.

The structure preferably contains organic fibers as an organic component. Organic fibers are fibrous substances containing organic components. Since the organic fibers are softer than the inorganic fibers described later, the fibers have the function of improving the toughness of the structure by intertwining the fibers with each other or bonding with other materials that may be contained in the structure. The organic fibers are preferably dispersed on at least the surface of the structure, and more preferably dispersed on the surface and inside of the structure. By dispersing the organic fibers on the surface of the structure, a network of fibers is formed on the surface of the structure. Compared with the structure of the prior art, the strength and toughness of the structure can be greatly improved, and the structure can be prevented from impact, bending, etc. Accidental rupture or destruction of a structure resulting from the occurrence of cracks. In this way, when the structural body is cut to a desired length, the damage of the structural body such as the occurrence of cracks or the progression of cracks can be suppressed, and the workability can be improved even when the structural body is processed and assembled. Wait.

The term "organic component" in this specification refers to a natural product or a compound having a hydrocarbon atomic group in its molecular structure. Therefore, a material composed of only carbon elements such as carbon fibers or containing carbon elements and nitrogen elements does not constitute the organic components and materials containing organic components in the present invention. Carbon fibers are classified into inorganic components to be described later.

Whether or not an organic component is included in the structure can be determined based on the presence or absence of peaks corresponding to C=C bonds, C-H bonds, C=O bonds, and O-H bonds obtained by solid-state NMR. Among these bonds, if there is at least a C-H bond or a C=O bond, it is determined that the material to be measured contains an organic component. In addition, whether or not the structure contains organic fibers can be determined by the above-mentioned solid-state NMR, and microscopic FT-IR and a microscope (manufactured by KEYENCE Co., Ltd., model: VHX-500, all microscopes in this specification are This) is judged by observing the surface and interior of the structure. In detail, the position where the functional group derived from the organic substance is mapped is confirmed by micro-FT-IR, and if organic fibers are observed at the position with a microscope, it is determined that organic fibers are included.

From the viewpoint of easier formation of a network structure of organic fibers, the content of the organic components including organic fibers in the structure is preferably more than 5% by mass, more preferably 5.5% by mass or more, based on the total amount, More preferably, it is 6 mass % or more. From the same viewpoint as above, the content of the organic fibers in the structure is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1% by mass or more.

Also, from the viewpoint of reducing the amount of gas generated during casting, the content of the organic components including organic fibers is preferably less than 20% by mass, more preferably less than 15% by mass, and still more preferably was less than 13% by mass. Within these ranges, the gas flowing into the target casting product can be reduced, and the quality of the casting can be improved. Moreover, it is possible to suppress the inconvenience of metal penetration, such as the molten metal sticking to the part after the thermal decomposition of the organic component derived from the structure. Furthermore, it is possible to suppress the backflow of the molten metal from the end face of the inflow port due to the backflow of the gas generated when the molten metal flows in during the casting process, thereby improving the safety of the casting operation. From the same viewpoint as above, the content of the organic fibers in the structure is preferably 10% by mass or less, more preferably 5% by mass or less, and still more preferably 2.5% by mass or less.

The content of the organic component in the structure for manufacturing a cast can be measured according to the following procedure when analyzing the structure for manufacturing a cast. As a pretreatment, FT-IR analysis was performed on a sample obtained by pulverizing and uniformly mixing the structure for manufacturing a casting to be measured. Furthermore, by comparing the detection intensities of the peaks derived from the C=C bond, the content of the inorganic components composed of only carbon such as carbon fibers contained in the structure was quantified. Then, the said sample was heated at the temperature of 1300 degreeC or more in nitrogen atmosphere, the organic component was carbonized, and the amount of mass loss was measured. Next, the carbonized sample was subjected to FT-IR analysis to quantify the content of the remaining carbon component. Finally, the total value of the value obtained by subtracting the carbon content of the sample after carbonization from the carbon content of the sample before carbonization and the amount of mass reduction are calculated, and the total value is used as the content of the organic component in the present invention.

Organic fibers include natural fibers, synthetic fibers, regenerated fibers, semi-synthetic fibers and recycled fibers. These can be used alone or in combination of two or more. Natural fibers include pulp fibers, animal fibers, and the like. Pulp fibers include wood pulp, non-wood pulp, and the like. Wood pulp includes mechanical pulp made from conifers or broad-leaved trees, and natural cellulose fibers made from conifers or broad-leaved trees. Non-wood pulp includes cotton pulp, lint pulp, hemp, cotton, bamboo, grass, and natural cellulose fibers using these as raw materials. Animal fibers include protein-based fibers such as wool, goat hair, cashmere, and feathers.

Examples of synthetic fibers include fibers containing synthetic resins such as polyolefin resins, polyester resins, polyamide resins, poly(meth)acrylic resins, polyethylene-based resins, polyimide resins, and aromatic polyamide resins. . These resins may be used alone or in combination to form one fiber. As a polyolefin resin, polyethylene, a polypropylene, etc. are mentioned, for example. As the polyester resin, for example, polyethylene terephthalate, polybutylene terephthalate, polybutylene naphthalate, polyhydroxybutyrate, polyhydroxyalkanoate, polycaprolactone may be mentioned. ester, polybutylene succinate, polylactic acid resin, etc. As a polylactic acid-type resin, a polylactic acid, a lactic acid-hydroxycarboxylic acid copolymer, etc. are mentioned, for example. As poly(meth)acrylic resin, polyacrylic acid, polymethyl methacrylate, polyacrylate, polymethacrylic acid, polymethacrylate, etc. are mentioned, for example. As the polyethylene-based resin, for example, polyvinyl chloride, polyvinylidene chloride, vinyl acetate resin, vinylidene chloride resin, polyvinyl alcohol, polyvinyl acetal, polyvinyl butyral, polyvinyl Styrene, etc.

As a regenerated fiber, cupro fiber, rayon, etc. are mentioned, for example. As a semi-synthetic fiber, cellulose acetate etc. are mentioned, for example. As recycled fibers, pulp fibers obtained by cutting and opening fibers such as waste paper and clothing can be mentioned. Among these, from the viewpoints of improving the toughness of the structure, improving the workability, and easily reducing the defects on the surface of the structure at the time of manufacture and casting of the structure, it is preferable to use pulp fibers, fibers containing polyester resin, and At least one of fibers containing an aromatic polyamide resin is used as the organic fiber.

From the viewpoint of improving the formability of the structure and improving the handleability, it is preferable that the structure further contains other organic components other than organic fibers. As a material containing such other organic components, starch, a thermosetting resin, a coloring agent, a heat-expandable particle, etc. are mentioned. These can be used alone or in combination of two or more. From the viewpoint of suppressing combustion of the structure during casting and improving the shape retention of the structure, it is preferable to use a thermosetting resin.

Thermosetting resins include phenol resins, modified phenol resins, epoxy resins, melamine resins, furan resins, and the like. Phenolic resins include novolac type, resol type, and the like. Modified phenol resins include those modified with urea, melamine and epoxy resin in addition to phenol. These can be used alone or in combination of two or more. Among these, it is preferable to use a phenol resin as the other organic component from the viewpoint of reducing gas generation during casting and easily obtaining a casting with high dimensional stability and surface smoothness.

The structure preferably further contains an inorganic component, and more preferably further contains inorganic particles as the inorganic component. By containing inorganic components in the structure, the heat resistance of the structure can be improved, and the strength, dimensional stability and shape retention of the structure during casting can be improved. When inorganic particles are included in the structure, the inorganic particles are preferably present at least on the surface of the structure, more preferably both on the surface and the interior of the structure. When inorganic particles are included, the inorganic particles include those whose melting point is preferably 1200°C or higher, more preferably 1500°C or higher. By using inorganic particles having such a melting point, the shape retention of the structure is excellent even under high temperature conditions during casting. The melting point of inorganic particles includes those that are actually 2500°C or lower. If the melting point of the inorganic particles is within the above-mentioned range, the structure for producing a cast product does not melt significantly during casting, and the occurrence of gas defects and metal penetration in the cast product can be suppressed.

The melting point of the inorganic particles was measured by the following method. Using a differential thermal balance-mass analyzer (TG-DTA/MS) manufactured by NIPPON STEEL TECHNOLOGY Co., Ltd., the structure for casting production was heated from 30°C to 1500°C at 20°C/min under a nitrogen atmosphere, and the temperature was increased for 30 minutes. Minutes later, it measured by cooling to 30 degreeC at 20 degreeC/min. Based on the measurement results, the melting point of the inorganic component contained in the structure for manufacturing a cast is determined.

Moreover, it is preferable that the structure contains one or two or more compounds selected from the group consisting of oxides, carbides, and nitrides of elements selected from aluminum, zirconium, silicon, and iron. That is, the structure preferably contains one or two compounds selected from the group consisting of aluminum oxide, silicon dioxide, iron(II) oxide, iron(III) oxide, aluminum nitride, zirconium oxide, silicon nitride, and silicon carbide. more than one species. By including these compounds in the structure, the heat resistance of the structure is improved even under high temperature conditions during casting, and the shape retention of the structure is also excellent. In addition, the inclusion of these compounds in the structure essentially means that the structure includes inorganic particles. The inclusion of the above-mentioned compound in the structure can be determined by X-ray diffraction measurement. As a specific procedure, by measuring the structure of the object to be measured under the conditions of a tube voltage of 30 kV, a tube current of 15 mL, a goniometer scan angle of 5 to 70°, and a goniometer scan speed of 10°/min, it can be determined that The presence or absence and type of the above compounds.

In addition to the inorganic particles which may have the above-mentioned melting point, clay minerals may also be contained. Clay minerals are typically those with a melting point of less than 1200°C. By further using inorganic particles having such a melting point, the clay minerals are melted when the molten metal is poured in, so that the inorganic particles can be filled between the inorganic particles and the inorganic particles can be prevented from being separated from each other. As a result, the strength and shape of the structure can be maintained.

The shapes of the inorganic particles are independent of each other, and may be spherical, polyhedral, scaly, lamellar, fusiform, fibrous, amorphous, or a combination thereof. The inorganic particles may be used alone or in combination of two or more.

In the following description, as the inorganic particles that can be included in the structure, a case where both the first inorganic particle and the second inorganic particle are used will be exemplified. The first inorganic particles and the second inorganic particles are different from each other in at least one of specific shapes and physical properties.

The first inorganic particles in one embodiment are preferably non-layered particles (ie, particles having shapes other than layered). In addition, the second inorganic particles in one embodiment are preferably layered particles. The melting point of the first inorganic particles in another embodiment is preferably 1200° C. or higher. Moreover, it is preferable that the melting point of the 2nd inorganic particle in another embodiment is less than 1200 degreeC. The melting point of the first inorganic particles in another embodiment is preferably 1200° C. or higher, and more preferably non-layered particles. Moreover, it is preferable that the melting point of the 2nd inorganic particle in another embodiment is less than 1200 degreeC, and it is more preferable that it is a layered particle. In this way, by using a plurality of inorganic particles each having a plurality of physical properties and each of which is different from each other, the strength and handleability of the structure can be improved. Unless otherwise specified, the following descriptions are appropriately applied to the descriptions in each of the above-described embodiments.

Regarding the first inorganic particles, it is preferable to use one or more of graphite, mullite, obsidian, zirconium, silica, fly ash, and alumina as the first inorganic particles from the viewpoint of further improving the heat resistance of the structure. 1. Inorganic particles, preferably at least graphite and mullite are used. Mullite contains alumina, silica and iron oxide. Generally, graphite is classified into naturally produced graphite such as flake graphite or earthy graphite, and artificial graphite artificially produced from petroleum coke, carbon black or pitch, etc. Among these graphites, it is preferable to use scaly graphite from the viewpoint of improving the formability of the structure.

The average particle diameter of the first inorganic particles is preferably 1 μm or more, more preferably 10 μm or more, from the viewpoint of improving the air permeability of the structure and suppressing gas defects in the casting. In addition, the average particle diameter of the first inorganic particles is preferably 1000 μm or less, more preferably 500 μm or less, from the viewpoint of maintaining a sufficient thermal strength of the structure even during casting. In order to keep the average particle diameter of the inorganic particles within the above range, for example, the inorganic particles used as raw materials can be sieved, or further pulverization can be performed using a known pulverizing device such as dry pulverization or wet pulverization.

The average particle size of the first inorganic particles can be obtained by measuring the particle size distribution using, for example, a laser diffraction/scattering particle size distribution analyzer (LA-950V2, manufactured by HORIBA, Ltd.). The particle size distribution is measured by using a dry cell as an accessory to measure the particle size of the inorganic particles in a powder state dispersed by compressed air. The measurement conditions are that the pressure of the compressed air is set to 0.20 MPa, the flow rate is set to 320 L/min, and the input amount can be adjusted so that the absorbance of the laser is 95% to 99%, and the sample is measured. From the obtained volume-based particle size distribution, the median value of the particle size was calculated and defined as the average particle size.

When the second inorganic particles are included as the inorganic particles, the second inorganic particles are preferably layered clay minerals. That is, the structure preferably contains layered particles as the second inorganic particles, and more preferably contains layered particles of clay minerals. Since the layered clay minerals swell due to the inclusion of water, the viscosity-increasing effect can be obtained, so the raw materials of the structure are easily mixed uniformly when the structure is manufactured. In addition, during drying, the layered clay minerals lose the water molecules existing between the unit crystal layers, and the inorganic particles and organic fibers form a compact structure while solidifying, thereby increasing the strength of the structure at room temperature and improving the handling. properties, and can effectively impart thermal strength to the casting. In addition, the workability and shape retention of the structure can be maintained, and the surface smoothness of the produced casting can be high, and the occurrence rate of gas defects can be reduced.

From the viewpoint of producing a structure having both heat resistance and strength of the structure, and excellent workability, dimensional stability, and shape retention during the production, handling, and casting of the structure, as an inorganic As for the particles, spherical particles and layered particles are preferably used in combination. More specifically, as the inorganic particles, it is preferable to use a combination of the first inorganic particles that are non-layered particles such as spherical particles, and the layered clay mineral particles that are the second inorganic particles that are layered particles. In order to confirm that spherical particles and layered particles are included in the structure, it can be determined by observing the shape of the particles on the surface of the structure using a scanning electron microscope (SEM).

The layered clay minerals that can be used as the second inorganic particles have the function of imparting formability to the structure by interposing the layered clay minerals between organic fibers or other materials, thereby improving the strength at room temperature and thermal strength. As the layered clay mineral, a crystalline inorganic compound having a layered structure represented by a layered silicate mineral can be used. Layered clay minerals can be natural or artificial.

Specific examples of the layered clay minerals include clay minerals represented by the kaolinite group, the bentonite group, and the mica group. These various layered clay minerals may be used alone or in combination of two or more. As a clay mineral of the kaolinite family, for example, kaolinite can be mentioned. Examples of the clay minerals of the bentonite family include montmorillonite, bentonite, saponite, lithium bentonite, aluminum bentonite, stevensite, and nontronite. As a clay mineral of mica group, vermiculite, halloysite, tetra silicic mica, etc. are mentioned, for example. Moreover, aluminum magnesium carbonate etc. can also be used as a layered double hydroxide. Among the above-mentioned layered clay minerals, montmorillonite or bentonite has a strong binding force with each component in a water-containing state, and is suitable for use from the viewpoint of shape imparting properties at the time of molding when producing a structure. Moreover, from the viewpoint of heat resistance at the time of casting, kaolinite or montmorillonite is suitably used.

The average particle diameter of the second inorganic particles is preferably 0.1 μm or more, more preferably 1 μm or more, from the viewpoint of improving the air permeability of the structure and suppressing gas defects in the casting. From the viewpoint of improving the strength, formability, and shape retention of the structure, the average particle diameter of the second inorganic particles is preferably 500 μm or less, more preferably 200 μm or less. When the layered clay mineral is used as the second inorganic particles, the average particle diameter of the layered clay mineral can be within the above-mentioned range. The average particle diameter of the second inorganic particles can be measured by the same method as the method for measuring the average particle diameter of the first inorganic particles described above.

The mass reduction rate of the structure in a high temperature environment such as casting is within a specific range. The mass reduction rate of the structure correlates with the gas generation rate due to the organic components in the structure during casting. Specifically, the lower the mass reduction rate, the lower the gas generation rate tends to be. Therefore, the smaller the mass reduction rate, the more stably the thermal strength of the structure can be maintained, and the dimensional accuracy of the manufactured casting can be maintained, or the reduction of the gas generated during casting. Excellent in gas defects and reduction of metal penetration of the structure to the casting surface.

Specifically, the mass reduction rate of the structure after heating at 1000° C. for 30 minutes under a nitrogen atmosphere is preferably less than 20%, more preferably less than 15% by mass, and still more preferably less than 9% by mass. If the mass reduction rate is within this range, the amount of gas generated when the high-temperature melt flows in the casting process will be reduced, and the gas flowing into the cast product will be reduced, so the quality of the cast will be further improved. Moreover, it is possible to suppress the inconvenience of metal penetration, such as the molten metal sticking to the part after the thermal decomposition of the organic component derived from the structure. Furthermore, it is possible to suppress the backflow of the molten metal from the end face of the inflow port due to the backflow of the gas generated when the molten metal flows in during the casting process, thereby improving the safety of the casting operation. In addition, in order to effectively reduce the gas generation rate, the above-mentioned mass reduction rate is preferably as low as possible, but from the viewpoint of sufficiently preventing the disintegration of the structure due to the increase in the toughness of the organic fiber, it is preferable. It is 1 mass % or more, More preferably, it is 3 mass % or more, More preferably, it is more than 5 mass %. In order to achieve such a mass reduction rate, for example, the content of the organic component including organic fibers or each inorganic particle can be set to the above-mentioned suitable range, or the gas generating component can be removed by heat treatment after forming in the production step of the structure. deal with.

Regarding the mass reduction rate, a thermogravimetric measuring apparatus (manufactured by Seiko Instruments Co., Ltd., STA7200RV TG/DTA) was used to heat the structure to be measured from 30°C at a temperature increase rate of 20°C/min to 20°C/min under nitrogen atmosphere. 1000°C for 30 minutes at 1000°C. At this time, based on the mass of the structure at 30°C (100%), the change in mass at 1000°C was measured as a function of temperature, and the percentage of the mass of the structure at 1000°C relative to the mass of the structure at 30°C was calculated. The mass reduction rate (%) was calculated in the form.

Regarding the structure, the maximum bending stress measured as one of the indicators of the toughness possessed by the structure is preferably 9 MPa or more, more preferably 12 MPa or more. By having these maximum bending stresses, a structure with high toughness can be obtained, disintegration, cracking, and cracking of the structure can be prevented, and the handleability, shape retention, and dimensional stability of the structure can be improved. In addition, the maximum bending stress of the structure is preferably 50 MPa or less, more preferably 40 MPa or less, and still more preferably 30 MPa or less, from the viewpoint of improving both the workability of the structure and the workability at the time of casting. .

In addition, about the structure, the bending strain at the maximum bending stress (hereinafter, also simply referred to as "bending strain") measured as one of the indicators of the toughness of the structure is preferably 0.6% or more, more preferably 0.65% or more. By having these bending strains, a structure with high toughness can be obtained, the disintegration or cracking of the structure, and the occurrence of cracks can be prevented, and the handleability, shape retention and dimensional stability of the structure can be improved. In addition, although the bending strain of the structure is preferably as large as possible, it is actually preferably 8% or less, more preferably 6% or less, and still more preferably 4% or less.

The bending strain and the maximum bending stress of the structure can be measured according to the three-point bending test of JIS K7017 using a measuring device (manufactured by Shimadzu Corporation, universal testing machine AGX-plus). At this time, as the structural system of the measurement sample, a plate-shaped sample having a length of 60 mm × a width of 15 mm × a thickness of 2 mm was cut out for measurement. The maximum bending stress is the physical property value calculated by dividing the moment (the product of the load and the distance) imparted to the sample by the section coefficient of the sample during the three-point bending test. When the above-mentioned plate-shaped sample cannot be cut out from the size of the structure to be measured, a sample having an arbitrary size can be cut out for measurement.

The structure for cast production having the above constitution contains organic fibers, and the organic fibers have moderate flexibility or elasticity, so that the entanglement or bonding between organic fibers or between organic fibers and other materials can be improved, and the structure can be improved. Resilience of the body. As a result, the resistance to brittle failure is improved, and even in the case of manufacturing the structure, or during operations such as transportation, processing, and assembly, or under high temperature load during casting, the surface or interior of the structure can be suppressed. Disintegration defects or cracks and cracks occur, and the operability of the structure is improved. In addition, accidental disintegration or breakage of the sprue, which becomes a flow path for molten metal flowing into the mold during casting, can also be prevented. In particular, since the organic fibers exist on the surface of the structure, the organic fibers are intertwined with each other to form a network structure, which acts as a net covering the structure, so it can effectively suppress the disintegration defect or cracking of the surface of the structure. The occurrence of rupture.

In addition, even in the case of manufacturing the structure, during transportation, processing, assembly, etc., or in the case of accidental occurrence of small cracks or disintegration defects during casting, due to the presence of the network structure of organic fibers, it can be suppressed. With the further development of defects such as cracks, the structure can exhibit higher shape retention. Furthermore, by containing inorganic particles in the structure, it becomes one with high heat resistance that can withstand casting. As a suitable form of inorganic particles, materials other than clay minerals and clay minerals are used in combination, whereby the structure has excellent heat resistance, the structure exhibits high normal temperature strength and thermal strength, and has both properties derived from organic fibers. Excellent handleability of structures resulting from high toughness. In addition, by controlling the mass reduction rate of the structure within a specific range, when the structure is used as a mold for casting, it is possible to effectively reduce the metal penetration of the structure to the surface of the casting, or the casting of gas defects. material defect. As a result, a cast product excellent in dimensional accuracy and surface smoothness can be produced, and the production cost of the cast product can be reduced.

For the structure, it is also required to improve the operability during processing or assembly. When the toughness of the structure is low, when the structure is cut into a specific size, cracks, omissions, or cracks are easily formed in the structure. and other defective parts. With regard to a structure that is prone to such defective parts, when it is used for casting, the structure itself disintegrates from the defective part, or molten metal oozes out of the structure. As a result, the operability of these structures is poor, and the casting efficiency is also poor.

In this regard, since the structure of the present invention has a structure excellent in toughness, the structure can be easily cut with a cutter or the like to adjust the size and use, and it is not easy to form in the structure even when the cutting process is performed. Defective parts such as chapped or missing, cracked, etc. Furthermore, even when a plurality of structures are connected or assembled into one mold using a plurality of structures, it is difficult to form defective parts such as cracks, omissions, and cracks in each of the structures. As a result, the structure of the present invention is excellent in workability during processing or assembly.

From the viewpoint of improving the toughness of the structure, thereby effectively suppressing the occurrence of disintegration defects, cracks and cracks on the surface of the structure, and improving the operability during use, the structure is preferably organic fibers present on the surface of the structure. , and the number of organic fibers per unit area on the surface of the structure is preferably a specific value or more. Specifically, in the structure, there are preferably 50 or more organic fibers per 100 mm ² on the surface of the structure, more preferably 70 or more, and still more preferably 100 or more. In addition, the number of organic fibers present per 100 mm ² on the surface of the structure is actually 300 or less.

Regarding the number of organic fibers existing on the surface of the structure, first, the fibrous substances existing on the surface of the structure were determined to be organic fibers by the methods using the above-mentioned solid-state NMR, microscopic FT-IR and microscope. After that, the fiber observation image data obtained by observing the surface of the structure containing organic fibers with a microscope or SEM can use image processing software (manufactured by Sangu Shoji Co., Ltd., WinROOF, all the image processing software in this manual are for this purpose. species), the area of 100 mm ² was regarded as 1 field of view, and the arithmetic mean of the number of roots when measuring 3 or more fields of view was calculated. When measuring the number of organic fibers, for the area to be measured, an area of 100 ^mm2 can be observed at one time, or the number of observations can be divided into multiple times to observe an area of 100 ^mm2 , for example, an area of 10 ^mm2 can be observed 10 times. Wait.

From the point of view of easily contacting a plurality of other fibers or materials with a single fiber, improving the mutual entanglement of fibers or bonding with other materials, thereby improving the toughness of the structure, and improving the operability of the structure. The average fiber length L1 of the organic fibers on the surface of the structure is preferably 0.5 mm or more, more preferably 1 mm or more. The average fiber length L1 of the organic fibers present on the surface of the structure is preferably 7 mm or less, from the viewpoint of improving the formability of the structure during manufacture and improving the dimensional uniformity of the structure during manufacture and casting. It is preferably 5 mm or less, and more preferably 4 mm or less. Regarding the average fiber length L1 of the organic fibers, the fiber observation image data can be obtained by observing the surface of the structure with a microscope or SEM. Using image processing software, 50 fibers are used as the object, and one end to the other end of the fiber to be measured is measured. The arithmetic mean of the lengths was taken as the average fiber length.

In terms of increasing the contact area with other fibers or materials due to the increase in the surface area of the fibers, improving the mutual entanglement of fibers or bonding with other materials, thereby improving the toughness of the structure, and improving the operability of the structure. In other words, the average fiber diameter D1 of the organic fibers present on the surface of the structure is preferably 8 μm or more, more preferably 10 μm or more. The average fiber diameter D1 of the organic fibers present on the surface of the structure is preferably less than 40 μm from the viewpoint of improving the formability at the time of manufacturing the structure and improving the dimensional uniformity of the structure at the time of manufacturing and casting. More preferably, it is less than 35 μm, and still more preferably 30 μm or less. Regarding the average fiber diameter D1 of the organic fibers, the fiber observation image data can be obtained by observing the surface of the structure with a microscope or SEM. Using image processing software, 50 fibers selected at random are used as the object, and 5 positions of the fiber are measured for each fiber. The length perpendicular to the longitudinal direction of the fiber to be measured was measured, and the arithmetic mean value at that time was taken as the average fiber diameter.

From the viewpoint of improving the mutual entanglement of fibers or bonding with other materials, thereby improving the rigidity and strength of the structure, the average fiber length (unit: mm) of the organic fibers existing on the surface of the structure is relative to the average fiber length (unit: mm). The ratio of the fiber diameter (unit: mm), that is, the ratio of the value obtained by dividing the average fiber length L1 (unit: mm) by the average fiber diameter D1 (unit: μm) divided by 1000 is “1000×average fiber length L1/average The ratio of the fiber diameter D1" is preferably 10 or more, more preferably 30 or more, still more preferably 50 or more, and particularly preferably 100 or more. From the viewpoint of improving the formability at the time of manufacturing the structure and improving the dimensional uniformity of the structure at the time of manufacture and casting, the ratio of “1000×average fiber length L1/average fiber diameter D1” is preferably 260 or less, and further Preferably it is 230 or less.

In the range where the effect of this invention is exhibited, the structure for casting manufacture may further contain an inorganic fiber. In the case of including inorganic fibers, the inorganic fibers mainly have the function of maintaining the shape of the structure without burning during manufacture and casting. Inorganic fibers that can be used include man-made mineral fibers, ceramic fibers, and natural mineral fibers. Man-made mineral fibers include carbon fibers such as PAN (Polyacrylonitrile, polyacrylonitrile)-based carbon fibers and pitch-based carbon fibers, rock wool, and the like. These inorganic fibers may be used alone or in combination of two or more. Among them, carbon fibers are preferably used from the viewpoint of maintaining the shape and strength of the structure in a high-temperature environment at the time of casting. Carbon fibers are fibers that have no hydrocarbon radicals in their structure and contain carbon double bonds in their structure. Carbon fibers are typically composed of only carbon elements.

Whether or not inorganic fibers are included in the structure can be determined by the following method. First, elemental mapping and elemental mapping by scanning electron microscopy (SEM)-energy dispersive X-ray spectroscopy (EDX) analysis or microscopic FT-IR analysis are carried out on the fibrous objects existing on the surface of the structure as objects. analyze. Based on these analyses, the types of elements and the types and amounts of molecular bonds contained in the fibrous material were analyzed. According to these analyses, fibers containing C=C bonds are observed and the fibers do not contain both metal elements and oxygen elements, or fibers that do not contain C-H bonds, C=O bonds, and O-H bonds are observed. In this case, it is determined that the fibrous material is an inorganic fiber.

When the structure includes inorganic fibers, the average fiber length of the inorganic fibers is preferably 0.5 mm or more, and more preferably 1 mm or more, from the viewpoint of improving the formability and uniformity of the structure for cast production. Further, the average fiber length of the inorganic fibers is preferably 15 mm or less, more preferably 8 mm or less, and still more preferably 5 mm or less, from the viewpoint of improving the formability of the structure. Regarding the average fiber length of the inorganic fibers, first, the fibrous substances present as the inorganic fibers were determined and specified by the above-mentioned method for the fibrous substances existing on the surface of the structure. After that, 30 or more fibers were randomly selected from the two-dimensional screen when the inorganic fibers were observed under a microscope or SEM at a magnification of 50 times, and the lengths from one end to the other end were measured. The arithmetic mean thereof was taken as the average fiber length.

When the structure contains inorganic fibers, the average fiber diameter of the inorganic fibers is preferably 5 μm or more, and more preferably 10 μm or more, from the viewpoint of improving the formability and uniformity of the structure for cast production. In addition, the average fiber diameter of the inorganic fibers is preferably 30 μm or less, more preferably 20 μm or less, from the viewpoints of improving the formability of the structure and improving the dimensional uniformity of the structure during production and casting. More preferably, it is 15 μm or less. Regarding the average fiber diameter of inorganic fibers, after judging the presence of inorganic fibers in the same manner as the above-mentioned method for judging inorganic fibers, 30 or more inorganic fibers can be arbitrarily selected as the object, and the length direction of the fibers at 5 locations for each fiber is measured. The arithmetic mean of the orthogonal lengths was taken as the average fiber diameter.

In the range which does not impair the effect of this invention, the mold coating agent can be applied to the structure for casting manufacture in addition to the above-mentioned components. In this case, the structure for casting production includes a base material portion having the structure described above, and a surface layer formed on the surface of the base material portion by application of a mold coating agent or the like. The purpose of the mold coating agent is to improve metal penetration resistance, surface smoothness and mold release properties. As a mold coating agent, the material widely used for sand mold casting, shell mold casting, etc., such as a material containing refractory particles as a main raw material and containing as an organic component such as a thermosetting resin, silicone, etc., is mentioned, for example. Furthermore, the structure for casting manufacture of this invention is excellent in metal penetration prevention property, surface smoothness, and mold release property even when the surface layer is not formed by applying a mold coating agent.

Hereinafter, the manufacturing method of the structure for casting manufacture is demonstrated. This production method is roughly divided into the following steps: mixing an organic component including organic fibers, and inorganic components such as inorganic particles or inorganic fibers as needed, and a dispersion medium to prepare a structure precursor; The precursor is heated and pressed, and the structure precursor is formed while curing. In the following description, as a preferable form, the method of mixing an organic component containing an organic fiber and an inorganic particle, and producing a structure precursor is demonstrated.

First, an organic component including organic fibers, inorganic components such as inorganic particles, and a dispersion medium are mixed to prepare a structure precursor (mixing step). Specifically, an organic fiber as an organic component, a thermosetting resin, various inorganic particles, and a dispersion medium are uniformly mixed to prepare a structure precursor. The structure precursor contains organic fibers and thermosetting resins as organic components, various inorganic particles, and a dispersion medium, and is in the form of a dough. The so-called dough refers to a state in which it has fluidity and can be easily deformed by external force, and the mixed organic components, various inorganic components and dispersion medium are not easily separated.

The mixing of various organic components, various inorganic particles, and dispersion medium may be performed by one addition or by sequential addition in any order. From the viewpoint of the uniformity of mixing, it is preferable to add and mix various organic components and various inorganic particles by dry mixing in advance. The structure precursor can be produced by kneading, for example, manually or using a known kneading apparatus. When a kneading device is used, it is preferably a universal mixer, a kneader, a pressurized kneader, etc., which are suitable for mixing high viscosity such as slurry or dough. In the case of using a kneading device, for example, a pressurized kneader (manufactured by Nihon Spindle Manufacturing Co., Ltd.) can be used, and kneading can be performed at 6.1 rpm for 30 minutes.

The dispersion medium may, for example, be a solvent such as water, ethanol, or methanol, or an aqueous dispersion medium such as a mixed system of these. From the viewpoints of improving the dispersion stability and ease of handling of various materials, it is preferable to use water as a dispersion medium. The addition amount of a dispersion medium such as water is preferably 10 parts by mass or more and 70 parts by mass or less with respect to a total of 100 parts by mass of the solid content mixture containing various organic components and various inorganic particles.

In the case of containing the layered clay mineral as inorganic particles, the layered clay mineral is granular or powdery in its dry state, but by mixing with water, the layered clay mineral is mixed with the cations contained in the unit crystal layer of the layered clay mineral. Hydration, water molecules enter the interlayer. Regarding the layered clay minerals in the wet state, the distance between the unit crystal layers in the layered clay minerals increases due to the increase of water molecules, and it becomes swelled and becomes a viscous fluid. Since the fluidity of layered clay minerals has both fluidity and viscosity, it can easily enter between other components such as organic fibers or inorganic particles, and can function as a binder that binds these to each other.

From the viewpoints of improving the formability and toughness when manufacturing the structure, improving the handleability of the obtained structure, and reducing the defects of the structure, the content of the organic fibers in the structure precursor is preferably 10% relative to the total content of the solid content. 0.3 mass % or more, and more preferably 0.5 mass % or more. The content of organic fibers is preferably 10 mass % or less, and more preferably 5 mass % or less, from the viewpoint of reducing gas generation during casting and reducing defects of the casting when casting using the obtained structure. The average fiber length and the average fiber diameter of the organic fibers used can be used within the above ranges, respectively.

The content of the first inorganic particles relative to the solid content in the structure precursor is preferably 40% by mass from the viewpoint of making the shape retention, surface smoothness, and releasability good at the time of production of the structure and at the time of casting above, more preferably 60 mass % or more. In addition, the inorganic particle content relative to the solid content in the structure precursor is preferably 90 mass % or less from the viewpoint of effectively expressing the toughness of the structure and improving the handleability of the obtained structure, More preferably, it is 85 mass % or less. The average particle diameter of the used first inorganic particles can be used within the above-mentioned range.

When the structure contains the second inorganic particles, the content of the second inorganic particles relative to the solid content content in the structure precursor is preferably from the viewpoint of improving the formability of the structure for casting a casting. 1 mass % or more, more preferably 3 mass % or more, particularly preferably 5 mass % or more. In addition, from the viewpoint of suppressing the amount of gas generated from the structure during casting and reducing the rate of occurrence of gas defects in the casting when casting is performed using the obtained structure, the content of the solid content in the precursor of the structure is The second inorganic particle content is preferably 50 mass % or less, more preferably 30 mass % or less, and still more preferably 20 mass % or less. When the layered clay mineral is used as the second inorganic particles, the content of the layered clay mineral can be set to the above range. The average particle diameter of the used second inorganic particles can be used within the above-mentioned range.

The structure may not contain inorganic fibers, that is, the content of inorganic fibers in the structure may be 0% by mass, and the structure may also contain inorganic fibers. In the case of including inorganic fibers, the content of inorganic fibers is preferably more than 0 mass % and 20 mass % or less, and more preferably 16 mass % or less, more preferably 5 mass % or less, still more preferably 3 mass % or less. In the case of including a plurality of inorganic fibers, the content of the inorganic fibers is based on the total amount. The average fiber length and average fiber diameter of the inorganic fibers used can be used within the above ranges, respectively.

When carbon fibers are included as inorganic fibers, the content of carbon fibers is preferably 1 mass % or more, more preferably 2 mass % or more, from the viewpoint of improving the formability at the time of manufacturing the structure and the shape retention at the time of casting. Moreover, 20 mass % or less is preferable, and, as for content of carbon fiber, 16 mass % or less is more preferable.

From the viewpoint of improving the formability of the structure, the dough-like structure precursor can be supplied to an external force imparting mechanism and stretched to form a sheet (stretching step). The external force applying means is not particularly limited as long as it can stretch the structure precursor into a sheet shape. For example, the structure precursor can be supplied between a pair of stretching rolls, or between stretching rolls and a flat plate, and stretched . Before and after this step, the structure precursor is maintained in a state easily deformed by an external force.

Next, the dough-like or sheet-like structure precursor is heated and pressed with a stamping die, and the structure precursor is dried and solidified while being molded into a structure having the shape of the target mold (forming step). Thereby, a structure in which at least organic fibers are present on the surface of the structure can be obtained. The stamping die has a shape corresponding to the outer shape of the cast structure to be formed. By using the stamping die to heat and press the structure precursor, the shape of the stamping die is transferred to the structure precursor, and the moisture contained in the structure precursor is dehydrated, dried and solidified, and then shaped. It is a structure with the shape of the target mold. At the same time, the thermosetting resin which can be contained as an organic component is hardened. The structure after this step becomes less likely to be deformed by external force. The formed structure can be formed by having a cavity that opens to the outside, and a set of two split molds can be combined to form a casting mold, or it can be an integrally formed structure.

Water is dehydrated from the precursor of the structure by heating and pressing, whereby the layered clay minerals contained in the precursor lose the dispersion medium molecules such as water existing between the unit crystal layers. By losing the dispersing medium molecules, the layered clay minerals form a compact structure inside the structure together with inorganic components such as organic fibers and inorganic particles, while shrinking and solidifying. As a result, shear force is generated between organic fibers, layered clay minerals, and other inorganic particles, and it becomes difficult to deform by external force, and the shape retention of the structure can be effectively exhibited. Furthermore, with regard to the fiber length and fiber diameter of organic fibers, the particle diameters of various inorganic particles, and the fiber length and fiber diameter of inorganic fibers contained as needed, even after the process from the production of the structural precursor to the forming step. Mixing, swelling, drying, and heating and pressing, the fiber length, fiber diameter and particle size are also almost unchanged. Therefore, the fiber length and fiber diameter of various fibers used as raw materials, the particle size of various particles, and the various fibers existing in the structure are also almost unchanged. The fiber length, fiber diameter and particle size of various particles are roughly the same.

The heating temperature in the forming step is preferably 70° C. or higher, more preferably 100° C. or higher, from the viewpoint of easily removing a dispersion medium such as water from the structure precursor. The heating temperature in the forming step is preferably 250°C or lower, more preferably 200°C or lower. The heating time in the molding step is preferably 1 minute or more and 60 minutes or less under the condition of the above-mentioned heating temperature range from the viewpoint of production efficiency. The pressure applied in the forming step is preferably 0.5 MPa or more, more preferably 1 MPa or more, from the viewpoint of improving the formability of the structure. Moreover, from the viewpoint of improving the formability of the structure, it is preferably 20 MPa or less, more preferably 10 MPa or less.

From the viewpoint of reducing the gas defect of the casting due to the vapor derived from a dispersion medium such as water, the structure for manufacturing a cast preferably has a water content of 5% by mass or less, and more preferably It is 3 mass % or less. The moisture content in the structure for casting manufacture may be adjusted by the above-mentioned forming step, or may be adjusted by performing a drying step in addition to the heating and pressing step. In the case of performing the drying step, a well-known constant temperature bath, a hot air drying device, or the like can be used. In addition, the heating temperature and heating time in the drying step may be the same as those described above.

In the case of combining a casting mold including two sets of split molds into a casting mold, after the structure is fabricated to form a set of split molds according to the above method, the cavity side becomes the inner side. The method in turn joins the split mold, whereby the target mold can be produced. As a method of joining the divided molds, for example, a joining member such as a screw or a jig, a general-purpose adhesive, a sand mold that can cover a set of divided molds, or the like can be used for joining.

The thickness of the structure for casting casting can be appropriately set according to the shape of the target casting, but from the viewpoint of obtaining sufficient thermal strength and shape retention during casting, the thickness of at least the part in contact with the molten metal is preferably 0.2 mm or more, more preferably 0.5 mm or more, and still more preferably 1 mm or more. In addition, from the viewpoint of improving the ease of handling of the structure and reducing the amount of gas generated, it is preferably 10 mm or less, more preferably 5 mm or less. The thickness of the structure can be adjusted by appropriately changing the shape or pressure of the molding.

Since the cast manufacturing structure produced by the above steps contains organic fibers, it is lightweight and has high toughness, and the disintegration of the structure, the occurrence of cracks and cracks can be suppressed, and the handleability of the structure is also excellent. In addition, since the structure for manufacturing a cast product contains inorganic particles, it becomes lightweight and exhibits the required toughness, and at the same time, the heat resistance is improved, and the structure has both high room temperature strength and hot strength, and high shape retention. Casting structure for manufacturing. Furthermore, casting defects such as metal penetration of the structure to the casting surface and gas defects can be effectively reduced. As a result, a cast product excellent in dimensional accuracy and surface smoothness can be produced. It is possible to manufacture a cast with excellent dimensional accuracy or surface smoothness, which means that the post-processing for making the manufactured cast to a desired shape or dimensional accuracy can be reduced, and as a result, the manufacturing cost of the cast can be reduced.

The manufacturing method of the casting using the structure for casting manufacture can be performed by a general casting method. That is, molten metal is poured from the sprue formed in the structure for casting product manufacture, and casting is performed. And after completion|finish of casting, it cools to a specific temperature, the structure for casting manufacture is removed, and a casting is exposed. After that, post-processing such as trimming treatment may be performed on the casting as necessary.

As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not limited to the said embodiment, It is possible to combine each structure suitably. [Example]

Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the present invention is not limited by this embodiment.

[Example 1] Organic fibers (mechanical pulp) and thermosetting resins (phenol resin; resol resin) were used as organic components, mullite (spherical, average particle size: 30 μm) was used as the first inorganic particles, and layered Clay mineral particles (montmorillonite; manufactured by Guofeng Industrial Co., Ltd., Kunipia F, average particle diameter: 145 μm) were used as the second inorganic particles. In addition to this, PAN-based carbon fibers (manufactured by Mitsubishi Chemical Co., Ltd., PYROFILTR03CM A4G) were used as inorganic fibers. These materials were mixed in the ratios shown in Table 1 below to prepare a structure precursor, and a structure for casting production was produced according to the above-mentioned method. The obtained structure for casting was formed into two shapes: a flat plate with a thickness of 2 mm; and a cylindrical shape with an outer diameter of 50 mm, a length of 300 mm, and a thickness of 2 mm. Furthermore, each evaluation of the maximum bending stress and the bending strain at the time of the maximum bending stress, the mass reduction rate, the average fiber length and the average fiber diameter on the surface of the structure, which will be described later, were performed using the flat-shaped casting structure. Moreover, each evaluation of the handleability of the structure described later, casting, and the surface property of the surface of the casting after casting was performed using the cylindrical casting structure. The addition amount of water was made into 50 mass parts with respect to 100 mass parts of mixtures. The heating temperature and heating time of the structure precursor were set at 140° C. for 10 minutes, and the pressure in the forming step was set at 5 MPa. "Total organic components" in the table indicates the content of the organic components in the structure for casting production. In this example, the structure was not subjected to treatment such as coating, and there was no surface layer.

[Example 2] Fibers containing aramid resin (manufactured by Toray Co., Ltd., Kevlar (registered trademark) chopped fibers, 100% by mass of aramid resin) were used as organic fibers instead of mechanical pulp, and inorganic fibers were not used, except In addition, each material was mixed in the ratio shown in the following Table 1, and the structure for casting manufacture was manufactured in the same manner as Example 1.

[Example 3] A structure for casting production was produced in the same manner as in Example 1, except that newspaper waste paper pulp from which pulp fibers were extracted by water beating treatment was used instead of mechanical pulp as organic fibers, and the respective materials were mixed in the ratios shown in Table 1 below. .

[Example 4] Mechanical pulp as organic fibers and thermosetting resin (phenol resin; resol resin) were used as organic components, and obsidian with an average particle size of 27 μm (manufactured by KINSEI MATEC Co., Ltd., polyhedral shape, Nice Catch Flower #330) was used ) as the first inorganic particles. Obsidian contains alumina, silica and iron oxide. In addition to this, PAN-based carbon fibers (manufactured by Mitsubishi Chemical Co., Ltd., PYROFIL TR03CM A4G) were used as inorganic fibers. Except for this, each material was mixed in the ratio shown in the following Table 1, and the structure for casting manufacture was manufactured in the same manner as in Example 1.

[Example 5] Fibers containing polyester resin (fiber diameter 11 μm, fiber length 5 mm, polyester resin 100% by mass) were used as organic fibers instead of mechanical pulp, and inorganic fibers were not used, except that the ratios shown in Table 1 below were used Each material was mixed, and the structure for casting manufacture was manufactured in the same manner as in Example 1.

[Example 6] The materials were mixed in the ratios shown in Table 1 below to implement the In the same manner as in Example 1, a structure for producing a cast was produced.

[Comparative Example 1] The respective materials were mixed in the ratios shown in Table 1 below, except that organic fibers were not used as the organic component, and a structure for casting production was produced in the same manner as in Example 1.

[Comparative Example 2] A structure for casting production was produced in the same manner as in Example 1, except that only newspaper waste paper pulp was used instead of the combination of mechanical pulp and newspaper waste paper pulp as the organic component, and the respective materials were mixed in the ratios shown in Table 1 below. .

[Evaluation of Maximum Bending Stress and Bending Strain at Maximum Bending Stress] For the structures for the production of castings of the Examples and Comparative Examples, a plate-shaped measurement sample was taken out by the above method, and the maximum bending stress (MPa) and the maximum bending stress of the sample were measured according to the three-point bending test method of JIS K7017. Bending strain (%). The maximum bending stress and bending strain are indicators of the toughness of the structure for casting manufacturing. The higher the maximum bending stress and bending strain, the higher the toughness of the structure and the higher the operability of the structure. The results are shown in Table 1.

[Evaluation of mass reduction rate] The evaluation of the mass reduction rate of the structures for the production of castings of Examples and Comparative Examples was performed by using a thermogravimetric measuring apparatus (manufactured by Seiko Instruments Co., Ltd., STA7200RV TG/DTA). The structure was heated from 30°C to 1000°C at a heating rate of 20°C/min in a nitrogen atmosphere, the change in mass was measured as a function of temperature, and the mass reduction rate (%) based on the mass at 30°C was calculated. The results are shown in Table 1.

[Evaluation of the average fiber length and average fiber diameter on the surface of the structure] The evaluation of the average fiber length and the average fiber diameter of the organic fibers present on the surface of the structure for producing a cast in Examples and Comparative Examples was performed by the above-described method. The results are shown in Table 1.

[Evaluation of the number of fibers on the surface of the structure] The evaluation of the number of fibers of the organic fibers present on the surface of the structure for producing a cast in Examples and Comparative Examples was performed by the above-mentioned method. The results are shown in Table 1.

[Evaluation of the operability of the structure] The evaluation of the workability of the structure for cast production of the Example and the comparative example was performed by the following method. Specifically, a hand-held saw with a blade thickness of 1 mm and a vertical saw blade was used to cut at a position 50 mm away from the end face of the structure, and the length of the influence range (mm ). The shorter the sphere of influence length, the better the operability of the structure. The results are shown in Table 1 below.

[Evaluation of casting (back blowing height)] Castings were produced by pouring 25 kg of molten metal at 1350°C containing cast iron into the casting molds for 20 seconds using the structures for producing casts of the Examples and Comparative Examples as molds. At this time, the blowback height (mm) of the molten metal from the end face of the molten metal inflow port was measured. The lower the blowback height is, the more the gas generated from the structure for casting a casting can be suppressed when the molten metal flows in, the more the gas defects of the casting can be reduced, and the higher the safety of the casting operation is. The results are shown in Table 1 below.

[Surface evaluation of casting surface] Castings were produced by using the structures for producing casts of Examples and Comparative Examples as a mold, and pouring molten metal containing cast iron at 1350°C into the mold. The area ratio of the metal penetration portion formed at this time was calculated, and the surface property of the cast surface was evaluated. Specifically, on the surface of the casting at the contact portion between the structure for casting a casting and the obtained casting, the molten metal that flows in destroys the part where the structure for manufacturing a casting is fixed and is fixed, or entrains a part derived from the casting sand. The attached and fixed part is regarded as the metal penetration part, and the existence and extent of its existence are visually judged. Next, regarding the range of the metal penetration portion determined by the above method, a sheet with a fixed basis weight is cut according to the shape of each metal penetration portion, and the sum of the mass of the cut sheets is divided by the basis weight of the sheet, thereby Calculate the area of the metal penetration portion. The surface area of the cast is calculated by using a sheet with a fixed basis weight, coating the surface of the cast so that the sheets do not overlap each other, and dividing the mass of the sheet for coating by the basis weight of the sheet. The surface area of the casting. Then, the area ratio of the metal permeation part was calculated as the percentage (%) of the area of the metal permeation part with respect to the surface area of the casting. The lower the area ratio of the metal penetration portion, the less the metal penetration of the structure into the surface of the casting, the more excellent the dimensional accuracy or the surface smoothness of the casting. The results are shown in Table 1 below.

[Table 1] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 organic ingredients organic fiber Pulp fiber [mass %] 0.5 - 5.0 0.5 - - - 26.0 Fiber containing aromatic polyamide resin [mass %] - 3.0 - - - - - - Fibers containing polyester resin [mass %] - - - - 3.0 2.0 - - Average fiber length L1[mm] 1.6 1.5 2.0 1.8 1.1 1.2 - 2.0 Average fiber diameter D1 [μm] 30 13 30 30 11 11 - 30 1000×L1[mm]/D1[μm] ratio 53.3 115.4 66.7 60.0 100.0 109.1 - 66.7 Thermosetting resin Phenolic resin [mass %] 9.0 9.0 9.0 9.0 9.0 5.0 9.0 18.0 Total organic ingredients [mass %] 9.5 12.0 14.0 9.5 12.0 7.0 9.0 44.0 Inorganic ingredients 1st inorganic particle Mullite [mass %] 72.5 73.0 68.0 - 73.0 75.0 73.0 - Obsidian [mass %] - - - 72.5 - - - 48.0 shape spherical spherical spherical polyhedron spherical spherical spherical polyhedron Melting point [℃] 1850 1850 1850 1340 1850 1850 1850 1340 2nd inorganic particle Montmorillonite [mass %] 15.0 15.0 15.0 15.0 15.0 15.0 15.0 - shape lamellar lamellar lamellar lamellar lamellar lamellar lamellar - Inorganic fiber Carbon fiber [mass %] 3.0 - 3.0 3.0 - 3.0 3.0 8.0 Average fiber length [mm] 1.5 - 2.0 1.3 - 1.3 1.3 2.0 Average fiber diameter [μm] 7 - 7 7 - 7 7 7 Total inorganic components [mass %] 90.5 88.0 86.0 90.5 88 93.0 91.0 56.0 Total ingredients [mass %] 100 100 100 100 100 100.0 100 100 Mass reduction [%] 5.78 8.01 9.69 6.53 8.87 5.12 5.54 29.37 The number of organic fibers existing per 100 ^mm2 on the surface of the structure [piece] 92 100 or more 100 or more 100 or more 100 or more 100 or more - 100 or more JIS K7017 three-point bending test Maximum bending stress [MPa] 16.11 11.79 9.23 14.45 12.83 18.20 21.30 11.92 Bending strain at maximum bending stress [%] 1.15 1.69 1.24 1.03 1.75 0.68 0.55 1.11 Evaluation of the operability of the structure (influence range length [mm]) 0.3 0.2 0.5 0.4 0.2 0.0 50 0.2 Casting evaluation (back blow height [mm]) 100 90 120 110 100 70 110 730 Surface property evaluation of casting surface (area ratio of metal penetration portion [%]) 1 1 2 2 1 1 1 5

As shown in Table 1, since the structure for manufacturing a cast of the Example contains a specific amount of an organic component including organic fibers, the maximum bending stress and the bending strain are specific values as compared with the structure for manufacturing a casting of the comparative example. As described above, since the toughness of the structure is improved, it can be seen that the handleability of the structure is improved. Moreover, since the structure for manufacture of the cast of the Example contained a specific amount of organic components including organic fibers, the mass reduction rate of the structure was below a specific value, and it was also found that the gas defect of the obtained cast could be effectively reduced. In addition, the area ratio of the metal penetration portion of the structure for manufacturing the casting of the example is equal to or less than that of the comparative example, so it can be seen that the metal penetration of the structure to the surface of the casting can be effectively reduced, and the dimensional accuracy and the surface can be obtained. Casting with excellent smoothness.

Therefore, the structure for casting production of the present invention is excellent in handleability, and can reduce gas defects in the obtained casting and metal penetration on the surface of the casting. In particular, in the structures for manufacturing casts of Examples 1, 3 and 4, the amount of gas generation can be suppressed and bending stress can be increased by blending inorganic fibers with a small amount of organic fibers. In addition, the structure for producing a cast of Example 5 can sufficiently satisfy the bending characteristics by using only the organic fibers, and at the same time, the production cost of the structure can be greatly reduced. [Industrial Availability]

ADVANTAGE OF THE INVENTION According to this invention, it is excellent in workability, and can provide the structure for casting manufacture which can reduce the gas defect of a casting and the metal penetration which generate|occur|produces in the casting surface.

Claims (24)

A structure for manufacturing a cast, which contains an organic component, At least a part of the above-mentioned organic components is an organic fiber, The mass reduction rate of the structure for manufacturing a cast product after being heated at 1000° C. for 30 minutes in a nitrogen atmosphere is 1 mass % or more and less than 20 mass %, and The structure for manufacturing a cast satisfies at least one of the following (1), (2) and (3): (1) Inorganic particles comprising first inorganic particles that are non-layered particles and second inorganic particles that are layered particles; (2) Inorganic particles comprising first inorganic particles having a melting point of 1200°C or higher and second inorganic particles having a melting point of less than 1200°C; (3) The maximum bending stress measured in accordance with JIS K7017 is 9 MPa or more, and the bending strain at the maximum bending stress is 0.6% or more. The structure for producing a cast according to claim 1, comprising inorganic particles, the inorganic particles having a melting point of 1200°C or higher, preferably 1500°C or higher. The structure for manufacture of a casting product according to claim 1, comprising inorganic particles, and the inorganic particles include those having a melting point of 2500° C. or lower. The structure for casting manufacture according to claim 1, wherein the mass reduction rate is less than 20% by mass, preferably less than 15% by mass, more preferably less than 9% by mass. The structure for casting manufacture according to claim 1, wherein the mass reduction rate is 1 mass % or more, preferably 3 mass % or more, and more preferably 5 mass % or more. The structure for manufacturing a cast according to claim 1, wherein the maximum bending stress is 9 MPa or more, preferably 12 MPa or more. The structure for casting manufacture according to claim 1, wherein the maximum bending stress is 50 MPa or less, preferably 40 MPa or less, and more preferably 30 MPa or less. According to the structure for manufacturing a casting according to claim 1, the above-mentioned bending strain at the maximum bending stress is 0.6% or more, preferably 0.65% or more. According to the structure for manufacturing a casting according to claim 1, the above-mentioned bending strain at the maximum bending stress is preferably 8% or less, more preferably 6% or less, and still more preferably 4% or less. The structure for producing a cast according to claim 1, comprising inorganic particles, and the inorganic particles include one or more selected from the group consisting of alumina, silica, and iron oxide. The structure for manufacture of a casting product according to claim 1, comprising inorganic particles comprising at least one selected from the group consisting of spherical particles and layered particles. The structure for manufacturing a casting according to claim 1, wherein the organic fibers are present at 50 or more per 100 mm ² on the surface of the structure for manufacturing a casting, preferably at least 70, more preferably at 100 above. The structure for producing a casting according to claim 1, wherein the organic fibers are present in 300 or less per 100 mm ² of the surface of the structure. The structure for producing a cast according to claim 12, wherein the average fiber length L1 of the organic fibers present on the surface is 0.5 mm or more, more preferably 1 mm or more. The structure for producing a cast according to claim 12, wherein the average fiber length L1 of the organic fibers present on the surface is 7 mm or less, preferably 5 mm or less, more preferably 4 mm or less. The structure for producing a cast according to claim 12, wherein the average fiber diameter D1 of the organic fibers present on the surface is less than 40 μm, preferably less than 35 μm, more preferably 30 μm or less. The structure for producing a cast according to claim 12, wherein the average fiber diameter D1 of the organic fibers present on the surface is 8 μm or more, preferably 10 μm or more. The structure for producing a cast according to claim 12, wherein the ratio (1000×L1/D1) of the average fiber length of the above-mentioned organic fibers existing on the above-mentioned surface to the average fiber diameter of the above-mentioned organic fibers is 10 or more, preferably 30 or more, more preferably 50 or more, still more preferably 100 or more. The structure for casting production according to claim 12, wherein the ratio (1000×L1/D1) is 260 or less, preferably 230 or less. The structure for producing a cast according to claim 1, further comprising other organic components other than the above-mentioned organic fibers. The structure for producing a cast according to claim 1, wherein the organic fibers comprise one or more selected from the group consisting of pulp fibers, fibers containing polyester resins, and fibers containing aromatic polyamide resins. The structure for manufacturing a cast according to claim 1, wherein the content of the inorganic fibers contained in the structure for manufacturing a cast is 0 mass % or more and 20 mass % or less, preferably 16 mass % or less, more preferably 5 mass % or more. mass % or less, more preferably 3 mass % or less. The structure for manufacturing a cast according to claim 1, wherein the content of the organic component in the structure for manufacturing a cast is more than 5 mass %, preferably 5.5 mass % or more, more preferably 6 mass % or more. The structure for manufacturing a cast according to claim 1, wherein the content of the organic component in the structure for manufacturing a cast is less than 20% by mass, preferably less than 15% by mass, more preferably less than 13% by mass.